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Characterization of Greywater and Its Implication for Reuse: A Case Study of Peri-Urban and Unplanned Areas

R.J. Kimwaga

Abstract


The situation of water supply services in Kigogo (a peri-urban and unplanned area) in Dar es Salaam, Tanzania is poor. The area is served by water operator in Dar es Salaam, DAWASCO only twice a week. As a result, people find other alternative source of water like boreholes and shallow wells. Grey water (GW) res-use is increasingly seen as an alternative to water saving in household especially in water shortage/scarce areas of peri-urban and unplanned areas, like Kigogo area. Grey water is waste water generated from domestic process such as dish washing, bathing and laundry excluding water from toilets. Since GW re-use has potential in reducing the water consumption and therefore efficiency in the household level, despite of its high production in Kigogo area, there is no study on the GW re-use that has been done so far. The study was therefore conducted with specific objectives; to characterize (quantity and quality) of GW with view of it’s re-use and explore its implication for re-use. The GW quantity was obtained by using direct interview method. 40 households were selected where the members of households were interviewed on their water consumption per day which had ultimate direct GW production. The GW samples were analysed for BOD5, pH, Dissolved Oxygen, Electrical Conductivity, Faecal Coli form, Total Nitrogen and Suspended Solids and in accordance to the Standards Methods for Water and Wastewater Examination. The GW quantity was from three sources, namely bathrooms, laundry and the kitchen. The significant contribution of GW was from the bathrooms and laundry. The kitchen contributed only about 5% while the bathrooms and laundry contributed about 45% and 50% respectively of GW produced. The quality of the GW varied depending on its source. The results for FC show variation from various sources of grey water. Laundry had showed the highest FC (6 x 104no/100ml), kitchen 2.5 x104 no/100ml and bathroom 3 x 104no/100ml. Despite their variation in the FC content, the GW from different sources is very high from the standard required with specific reuse. For vegetable irrigation the standard allows the maximum FC of 1000no/100ml and for lawn irrigation it requires the water with FC not more than 5000 no/100ml. However, on the other aspect of GW re-use, i.e. quality, the study has found out that GW from Kigogo is not good enough for re-use; as it has higher FC than the required for reuse in irrigation of vegetables. According to WHO can be used for irrigation without restriction if the BOD is less than 25mg/l, TSS is less than 50mg/l and FC is less than 1000 no/100ml. The barriers to reuse of GW from Kigogo area is its quality. The study recommends treatment of GW prior to re-use by grey water towers.

Keywords


Grey water, Re-use, Quantity, Quality, Irrigation, Recycle

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